In a flexographic printing system, the inking roller inks a soft printing roller directly, i.e. a soft printing form, while, for example, in offset printing, a soft transfer roller is provided between the inking roller and the hard printing roller or printing form respectively.
An apparatus of the above-mentioned type is known from U.S. Pat. No. 4,428,291. Besides an inking roller and a transfer roller it has a separate wetting (moistening) roller. The wetting roller is arranged parallel to the inking roller and the transfer roller. It is in contact with the inking roller, and the surfaces of the inking roller and the wetting roller have roughly the same path speed. An engraving in the form of little individual cups (indentations) is provided in the inking roller. These cups are filled with coating medium upon the inking roller making contact with the wetting roller. The cups serve for metering (supplying) the coating medium. For this, a wiper (stripper) blade in contact with the surface of the inking roller, is also provided. The wiper blade wipes off the coating medium from the inking roller which is in excess of that required to fill the engraving on the inking roller. The metered coating medium is then transferred to the transfer roller by means of contact with such. The arrangement of the inking roller in the known apparatus, also designated screen (raster) roller, is comparatively expensive. For wearing purposes, the inking roller has a ceramic surface. However, in order to ensure the desired wetting properties of the coating medium on the inking roller, the cups of the engraving on the inking roller are lined with copper. From this it is quite clear that as well as being comparatively large, the inking roller is a complicated and expensive component. The size of the inking roller also interferes with the changing of the roller for altering the metering of the coating medium.